Final answer:
By applying the transitive property of equality to the given equations Lm=mp and Lm=9, we conclude that the value of mp is 9.
Step-by-step explanation:
In the given equation Lm = mp and Lm = 9, we are to find the value of mp. Since Lm is defined as both mp and the number 9, we can state that mp must also be equal to 9. This is because if one variable is equal to two different things, those two things must be equal to each other as per the transitive property of equality in mathematics. Therefore, the value of mp is 9, which corresponds to choice a) 9.